1. Field of the Invention
This invention relates to anticancer compositions in terms of the inhibition of growth of certain cancerous cell lines and in terms of apoptosis or programmed (or induced) cancer cell death. Specifically, the invention relates to certain heteroarotinoids and derivatives thereof.
2. Background
Retinoids (vitamin A and derivatives thereof) is a name associated with a family of compounds both of natural and synthetic origin. There is significant interest in such molecules because of the observed strong anticancer activity in a number of assays including the hamster tracheal organ culture (TOC) assay, the omithine decarboxylase (ODC) assay, and with HL-60 cells (human leukemic cell line). Heteroarotinoids are a group of derivatives that contain an aromatic ring and at least one heteroatom in a fused, partially saturated ring bonded to an aromatic ring.
Examples of heteroarotinoids and the activity of such in the assays cited above are found in several papers such as: Journal of Medicinal Chemistry, 1985, Vol. 28, pages 116-124, entitled xe2x80x9cSynthesis and Characterization of Selected Heteroarotinoidsxe2x80x94Pharmacological Activity as Assessed in Vitamin A Deficient Hamster Tracheal Organ Culturesxe2x80x94Single Crystal X-ray Diffraction Analysis of 4,4-Dimethylthiochrom-6-yl Methyl Ketone-1,1-Dioxide and Ethyl (E)-p-[2-(4,4-Dimethylthiochroma-6-yl)propenyl]benzoatexe2x80x9d, by K. M. Waugh, K. D. Berlin, W. T. Ford, E. M. Holt, J. P. Carrol, P. R. Schomber, and L. J. Schiff; Journal of Medicinal Chemistry, 1987, Vol. 30, pages 1174-1480, entitled xe2x80x9cHeteroarotinoids. Synthesis, Characterization, and Biological Activity in Terms of an Assessment of these Systems to Inhibit the Induction of Ornithine Decarboxylase Activity and to Induce Terminal Differentiation of HL-60 cellsxe2x80x9d, by L. W. Spruce, S. N. Rajadhyaksha, K. D. Berlin, J. B Gale, E. T. Miranda, W. T. Ford, E. C. Blossey, A. K. Verma, M. B. Hossain, D. van der Helm, and T. R. Breitman; and Journal of Medicinal Chemistry, 1991, Vol. 34, pages 430-439, entitled xe2x80x9cNovel Heteroarotinoids: Synthesis and Biological Activityxe2x80x9d, by L. W. Spruce, J. B. Gale, K. D. Berlin, A. K. Verma, T. R. Breitman, X. Ji, and D. van der Helm.
Another report entitled xe2x80x9cHeteroarotinoids; Crystal and Molecular Structure Analysis of Methyl (z)- and Methyl (E)-4-[2-(4,4-Dimethylthiochroman-6-yl)-1-propenyl]benzoatexe2x80x9d, in the journal entitled Structural Chemistry, 1991, Vol. 2, pages 515-522, by W. J. Welsh, V. Cody, K. Suwinska, K. D. Berlin, S. N. Radjadhyaksha, S. Subramanian, and A. K. Verma, contains background data pertinent to the invention as well. Other background information on heteroarotinoids is found in U.S. Pat. No. 4,826,984 (May 2, 1989), U.S. Pat. No. 4,883,254 (May 23, 1989) and U.S. Pat. No. 4,997,276 (Dec. 11, 1990). Summaries of the biochemistry, chemistry, and prior biological activity of retinoids, including the few heteroarotinoids known, are found in five treatises, namely xe2x80x9cChemistry and Biology of Synthetic Retiniodsxe2x80x9d, by M. I. Dawson and W. H. Okamura, editors, CRC Press: Boca Raton, Fla., 1990, xe2x80x9cThe Retinoidsxe2x80x9d, Volumes I and II, by M. B. Sporn, A. B. Roberts, and D. S. Goodman, editors, Academic Press: Orlando, Fla., 1984, xe2x80x9cThe Retinoidsxe2x80x9d, 2nd Edition, by M. B. Sporn, A. B. Roberts, and D. S. Goodman, editors, Raven Press: New York, N.Y., 1994, and xe2x80x9cRetinoidsxe2x80x9d, Fifth Edition, Vol. 3, by M. I. Dawson, Chp 44, in Burger""s Medicinal Chemistry and Drug Discovery, M. E. Wolff, editor, J. Wiley and Sons, Inc., New York, 1996.
More recent work in the general area includes: Journal of Medicinal Chemistry, 1999, Vol. 42, pages 3602-3614 entitled xe2x80x9cSynthesis, Structure-Activity Relationships, and RARxcex3-Ligand Interactions of Nitrogen Heteroarotinoidsxe2x80x9d by A. Dhar, S. Liu, J. Klucik, K. D. Berlin, M. M. Madler, S. Lu, R. T. Ivey, D. Zacheis, C. W. Brown, E. C. Nelson, P. J. Birckbichler, and D. M. Benbrook and Journal of Medicinal Chemistry, 1999, Vol. 42, pages 4434-4445, entitled xe2x80x9cHeteroarotinoids Inhibit Head and Neck Cancer Cell Lines in vitro and in vivo Through Both RAR and RXR Retinoic Acid Receptorsxe2x80x9d by D. Zacheis, A. Dhar, S. Lu, M. M. Madler, J. Klucik, C. W. Brown, S. Liu, F. Clement, S. Subramanian, G. M. Weerasekare, K. D. Berlin, M. A. Gold, J. R. Houch, Jr., K. R. Fountain, and D. M. Benbrook.
The heteroarotinoids described and claimed herein have not been, to the knowledge of the inventors, previously described in either the patent or literature art. As will be seen, the inventive heteroarotinoids significantly differ both in structure and activity as compared to known compounds. No assertion is made that the inventive heteroarotinoids activate the common retinoid receptors.
The present invention involves the synthesis and use of certain unusual heteroarotinoids which have varying abilities to inhibit growth of certain cancerous cells, induce normal cell differentiation, and induce apoptosis or death of cancerous cells. The inventive structures consist of a three atom urea or thiourea linker group with aryl substituents, one on each end of the group and bonded to each of the nitrogen atoms. One of the aryl substituents has at least one heteroatom in a fused, partially saturated ring. Thus, the inventive heteroarotinoids have in common the basic molecular unit shown below, wherein each aryl substituent is denoted Ar and W and Q denote the indicated alternatives: 
The inventive heteroarotinoids appear to be much less toxic than endogenous and synthetic retinoid standards, e.g. trans-retinoic acid, 9-cis-retinoic acid, 13-cis-retinoic acid, etretinate, acitretin, and 4-HPR, on the basis of gross examination in tissue cultures and in animal models. Moreover, the unique three-atom linkage endows the inventive molecules with a certain rigidity not possessed in heteroarotinoids having a conventional two-carbon ester linker group. This structural feature is reasoned to be important in the interaction of the molecules with nuclear receptors and is believed to contribute to decreased toxicity insofar as the body is well adept at processing urea derivatives.
The heteroarotinoids of the present invention are very peripherally related in structure to trans-retinoic acid, 9-cis-retinoic acid, and 13-cis-retinoic acid as illustrated. The inventive heteroarotinoids, shown in the general structures 1 and 2, have either oxygen or sulfur as the heteroatom, two aryl rings depending from the three atom linker (either urea or thiourea), and possess the indicated alternatives at G, R, X, Y and Z: 
More particularly, the present invention encompasses heteroarotinoids of the following formulas, wherein G, R, Q, W and Z denote the indicated alternatives:
Isomeric heteroarotinoids having the formulas: 
Isomeric heteroarotinoids having the formulas: 
Heteroarotinoids with only one geminal group of the formulas: 
Biological data generated from a large number of representative heteroarotinoids demonstrates significant inhibition of growth of three ovarian cancer cell lines, namely, Caov-3, SKOV-3, and OVCAR-3 cell lines. In addition, the inventive heteroarotinoids were tested against three cell lines of the cervix, namely, SiHa, HT-3, and C-33A, and one vulvar cell line, SW962, using t-RA, 9-c-RA and 4-HPR as controls, wherein a range of inhibitory prowess was observed with several of the heteroarotinoids outperforming the standards. Representative agents screened for apoptosis effect were as good or better than 9-c-RA in inducing apoptosis (cell death) of cancerous cells and were superior to 4-HPR, the clinically used agent. Xenograph investigations of representative heteroarotinoids using nude and immunocompromised mice injected with OVCAR-3 human carcinogenic cells were very demonstrative of the ability to reduce tumor volume and were comparable with that observed with 4-HPR. The concentrations used of the heteroarotinoids were in the microgram range. That the effect could be manifested at such a low concentration is suggestive of a low toxicity in mammals.
The heteroarotinoids according to the present invention hence find a use in therapy as antitumor agents, for the treatment or prophylaxis of benign, malignant, or metastatic neoplasms, as well as in the traditional indications for retinoids, such as skin disorders (acne, psoriasis), as well as degenerative disorders and/or inflammation of the mucosae.
The inventive heteroarotinoids may be readily provided in pharmaceutical compositions containing one or more of the heteroarotinoids, or of their addition salts with a pharmaceutically acceptable base or acid when a salifiable group is present, alone or in combination with one or more pharmaceutically acceptable, non-toxic, inert vehicles or excipients. Among such pharmaceutical compositions, there may be mentioned, more especially, those which are suitable for oral, parenteral, nasal, rectal, perlingual, ocular or respiratory administration, and in particular, tablets, simple or sugar-coated, sublingual tablets, sachets, packs, hard gelatin capsules, preparations to be dissolved under the tongue, bars, suppositories, creams, ointments, skin gels, injectable preparations or preparations to be swallowed, aerosols, eye or nose drops, and the like.
The appropriate dosage will vary according to an individual""s age and weight, the administration route and the nature of the therapeutic indication and of any associated treatments, but will be an amount effective to exert a therapeutic effect on a tumor by any mechanism such as by killing tumor cells, reducing cell proliferation or reducing the size of the tumor or, in the case of its use as a chemoprevention agent, an amount sufficient to exert a prophylactic effect or a preventative effect on recurrence after primary therapy, or a prevention of secondary tumors.
In another aspect of the invention, the inventive molecules may also find use as a sensitizing agent administered in advance of or conconcurrently with a chemotherapeutic agent to increase the selectivity and/or efficacy of the chemotherapeutic agent. In this respect an effective amount refers to amounts of the inventive heteroarotinoids capable of sensitizing tumor cells to treatment by one or more chemotherapy agents, including cisplatin, carboplatin, VP 16, teniposide, daunorubicin, doxorubicin, dactinomycin, mitomycin, plicamycin, bleomycin, procarbazine, nitrosourea, cyclophosphamide, bisulfan, melphalan, chlorambucil, ifosfamide, merchlorehtamine, taxol, taxotere, anthracyclines, and ionizing radiation.
A better understanding of the present invention, its several aspects, and its advantages will become apparent to those skilled in the art from the following detailed description, taken in conjunction with the attached drawings, wherein there is shown and described the preferred embodiment of the invention, simply by way of illustration of the best mode contemplated for carrying out the invention.